1. Field of the Invention
The present invention relates to circuit modules and measurement methods and more specifically relates to circuit modules that include a processing circuit and an isolator and measurement methods.
2. Description of the Related Art
A composite electronic component described in Japanese Unexamined Patent Application Publication No. 2005-117500 is a known example of a conventional circuit module. The composite electronic component described in Japanese Unexamined Patent Application Publication No. 2005-117500 includes a power amplifier and an isolator. The isolator is provided downstream of the power amplifier and plays the role of preventing a signal from entering the power amplifier in a reverse direction.
In the case of the above-described composite electronic component, at the time of manufacture, the electrical characteristics of the isolator are adjusted while measuring the large signal characteristics of the composite electronic component serving as a power amplifier in order to make the measured values of the isolator become desired values. Thus, desired electrical characteristics are obtained for the isolator.
However, there is a problem with the composite electronic component described in Japanese Unexamined Patent Application Publication No. 2005-117500 in that the isolation characteristics of the isolator cannot be accurately measured while the isolator is being used inside the composite electronic component. In more detail, measurement of the isolation characteristics of the isolator is performed by inputting a test signal from an output port of the isolator and measuring an output signal output from an input port of the isolator. However, in the above-described composite electronic component, since the power amplifier and the isolator are connected to each other, a test signal is input from an output port of the isolator and an output signal is measured from an input signal of the power amplifier. Consequently, the isolation characteristics of the composite electronic component and the isolation characteristics of the isolator are superposed on top of one another. Thus, in the composite electronic component described in Japanese Unexamined Patent Application Publication No. 2005-117500, there is a concern that the isolation characteristics of only the isolator cannot be measured.